Protective device with separate end-of-life trip mechanism

ABSTRACT

The present invention is directed to a protective wiring device for use in an electrical distribution system. The device includes a plurality of line terminals and a plurality of load terminals configured to be coupled to the plurality of line terminals in a reset state. A detector circuit is coupled to the plurality of line terminals. The detector circuit is configured to generate a detection signal in response to detecting at least one predefined perturbation in the electrical distribution system. A circuit interrupter assembly is coupled between the plurality of line terminals and the plurality of load terminals. The circuit interrupter assembly is configured to decouple the plurality of line terminals from the plurality of load terminals in response to the detection signal. An end-of-life mechanism is coupled to the detector circuit. The end-of-life mechanism is configured to permanently decouple the plurality of line terminals from the plurality of load terminals in the absence of an intervening signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. patent application Ser. No.11/025,509 filed on Dec. 29, 2004 now abandoned, U.S. patent applicationSer. No. 10/900,769 filed on Jul. 28, 2004 now U.S. Pat. No. 7,154,718,and U.S. patent application Ser. No. 10/942,633 filed on Sep. 16, 2004now U.S. Pat. No. 7,173,799, the contents of which is relied upon andincorporated herein by reference in their entirety, and the benefit ofpriority under 35 U.S.C. §120 is hereby claimed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to electrical wiring devices,and particularly to electrical wiring devices having protectivefeatures.

2. Technical Background

Examples of electric circuit protection devices include ground faultcircuit interrupters (GFCIs), arc fault circuit interrupters (AFCIs), ordevices that include both GFCIs and AFCIs in one protective device. Anelectric circuit typically includes at least one protection devicedisposed in the breaker box, in a duplex receptacle, in an electricalplug, or the like. The most common fault conditions are ground faultsand arc faults. The function of a protection device is to detect thefault and then remove power to the load circuit to substantiallyeliminate the possibility of shock or fire.

An arc fault is a discharge of electricity between two or moreconductors. There are two types of arc faults. One type is a parallelarc fault, and the other is known as a series arc fault. A parallel arcfault is caused by damaged insulation on the hot line conductor orneutral line conductor, or on both the hot line conductor and theneutral line conductor, such as from an overdriven staple. The damagedinsulation may cause an arc between the two conductors and may result ina fire. A series arc may be caused by a break in the line or neutralconductors of the electrical distribution system or by a loose wiringdevice terminal. An arc fault usually manifests itself as a highfrequency current signal that typically exhibits a concentration ofenergy in certain frequency bands. As such, AFCIs may be configured todetect arc faults by being designed to recognize the aforementioned highfrequency signature.

A ground fault, on the other hand, is a condition that occurs when acurrent carrying (hot) conductor contacts ground to create an unintendedcurrent path. The unintended current path represents an electrical shockhazard. A ground fault may also represent a fire hazard. A ground faultmay occur for several reasons. If the wiring insulation within a loadcircuit becomes damaged, the hot conductor may contact ground, creatinga shock hazard for a user. A ground fault may also occur when equipmentcomes in contact with water. A ground fault may also be caused bydamaged insulation within the facility.

Under normal operating conditions, the current flowing in the hotconductor should equal the current in the neutral conductor. A groundfault upsets this balance and creates a differential current between thehot conductor and the neutral conductor. GFCIs exploit this phenomenonby comparing the current in the hot conductor(s) to the return currentin the neutral conductor. In other words, a ground fault is typicallydetected by sensing the differential current between the two conductors.Upon detecting a ground fault, the GFCI may respond by actuating analarm and/or interrupting the circuit.

A grounded neutral condition is another type of fault condition thatoccurs when the load neutral terminal, or a conductor connected to theload neutral terminal, becomes grounded. While this condition does notrepresent an immediate shock hazard, it is nonetheless an insidiousdouble-fault condition that may lead to a serious injury or a fatality.The reasons for this become apparent when one considers that GFCIs areconfigured to trip when the differential current is greater than orequal to approximately 6 mA. However, when the load neutral conductor isgrounded the GFCI becomes de-sensitized because some of the return pathcurrent is diverted to ground. Under these conditions, it may take up to30 mA of differential current before the GFCI trips. Accordingly, when afault occurs in a grounded neutral state, the GFCI may fail to trip,exposing a user to experience serious injury or death. There are otherreasons why a protective device may fail to perform its function.

The protective device includes electronic and mechanical components thatmay experience an end-of-life (EOL) condition. For example, protectivedevices must include some type of fault sensor and detector. Thedetector output is coupled to an electronic switch. When the switch isturned ON a solenoid is energized. The energized solenoid drives acircuit interrupter in turn. Of course, the circuit interrupterdisconnects the load terminals from the line terminals when a fault isdetected. Component failure may occur for a variety of reasons. Failuremay occur because of the normal aging of electronic components.Mechanical parts may become corroded, experience mechanical wear, orfail because of mechanical abuse. Devices may also fail when they areoverloaded when installed. Electrical power surges, such as fromlightning, also may result in failure. If any of the sensor, thedetector, the switch, solenoid, and/or power supply fail, i.e., an EOLcondition is extant, the GFCI may fail to trip, exposing a user toexperience serious injury or death. There are other reasons why aprotective device may fail to perform its function. Accordingly, aprotection device that denies power to a load circuit in the event of anEOL condition is desirable.

In one approach that has been considered, a protective device isequipped with a manually activated test button for determining theoperating condition of the device. If the test fails the circuitinterrupter permanently disconnects the load terminals from the lineterminals. One drawback to this approach relates to the fact that thedevice only reacts to a problem if the user activates the test button.As such, this approach does not address the aforementioned EOL scenario.Another drawback to this relates to the fact that even if the device ismanually tested, an inoperative circuit interrupter allows a fire orshock hazard to persist indefinitely.

In another approach that has been considered, a protective device may beequipped with an automatic test feature. In this approach, the automatictest mechanism periodically tests the device without user intervention.A failed test automatically causes the circuit interrupter topermanently disconnect the load terminals from the line terminals. Thedrawback to this approach is similar to the manual approach describedabove. The auto-test device also provides unprotected power to the loadcircuit when the circuit interrupter is experiencing an EOL condition.

Accordingly, a protective device is needed having a test feature fordetecting failure of both electrical components and electro-mechanicalcomponents. Further, what is needed is a device having a separate testmechanism configured to deny power to a load circuit in response to theaforementioned EOL conditions.

SUMMARY OF THE INVENTION

The present invention addresses the needs described above. As such, thepresent invention is directed to a protective device that has a testfeature for detecting failure of both electrical components andelectro-mechanical components. The protective device of the presentinvention also includes a separate test mechanism configured to denypower to a load circuit in response to the aforementioned EOLconditions.

One aspect of the present invention is directed to a protective wiringdevice for use in an electrical distribution system. The device includesa plurality of line terminals and a plurality of load terminalsconfigured to be coupled to the plurality of line terminals in a resetstate. A detector circuit is coupled to the plurality of line terminals.The detector circuit is configured to generate a detection signal inresponse to detecting at least one predefined perturbation in theelectrical distribution system. A circuit interrupter assembly iscoupled between the plurality of line terminals and the plurality ofload terminals. The circuit interrupter assembly is configured todecouple the plurality of line terminals from the plurality of loadterminals in response to the detection signal. An end-of-life mechanismis coupled to the detector circuit. The end-of-life mechanism isconfigured to permanently decouple the plurality of line terminals fromthe plurality of load terminals in the absence of an intervening signal.

In another aspect, the present invention is directed to a protectivewiring device for use in an electrical distribution system. The deviceincludes at least one line terminal and at least one load terminalconfigured to be coupled to the at least one line terminal in a resetstate. A detector circuit is coupled to the at least one line terminal.The detector circuit is configured to generate a detection signal inresponse to detecting at least one predefined perturbation in theelectrical distribution system. A circuit interrupter assembly iscoupled between the at least one line terminal and the at least one loadterminal. The circuit interrupter assembly is configured to decouple theat least one line terminal from the at least one load terminal inresponse to the detection signal. An end-of-life mechanism is coupled tothe detector circuit. The end-of-life mechanism is configured topermanently decouple the at least one line terminal from the at leastone load terminal in the absence of an intervening signal. A testcircuit is coupled to the detector circuit, the test circuit beingconfigured to generate a test signal. The test signal simulates the atleast one predefined perturbation A checking circuit is coupled to thedetector circuit. The checking circuit is configured to generate theintervening signal in response to the detection signal.

In yet another aspect, the present invention is directed to a protectivewiring device for use in an electrical distribution system. The deviceincludes at least one line terminal and at least one load terminalconfigured to be coupled to the at least one line terminal in a resetstate. A detector circuit is coupled to the at least one line terminal.The detector circuit is configured to generate a detection signal inresponse to detecting at least one predefined perturbation in theelectrical distribution system. A circuit interrupter assembly iscoupled between the at least one line terminal and the at least one loadterminal. The circuit interrupter assembly is configured to decouple theat least one line terminal from the at least one load terminal inresponse to the detection signal. A test circuit is coupled to thedetector circuit, the test circuit being configured to generate a testsignal. The test signal simulates the at least one predefinedperturbation. A circuit element is coupled between the end-of-lifemechanism and the at least one load terminal. The circuit element isconfigured to transmit the intervening signal from the at least one loadterminal to the end-of-life mechanism. The intervening signal issubstantially equal to zero volts.

In yet another aspect, the present invention is directed to a protectivewiring device for use in an electrical distribution system. The deviceincludes at least one line terminal and at least one load terminalconfigured to be coupled to the at least one line terminal in a resetstate. A detector circuit is coupled to the at least one line terminal.The detector circuit is configured to generate a detection signal inresponse to detecting at least one predefined perturbation in theelectrical distribution system. A circuit interrupter assembly iscoupled between the at least one line terminal and the at least one loadterminal. The circuit interrupter assembly is configured to decouple theat least one line terminal from the at least one load terminal inresponse to the detection signal. A test circuit is coupled to thedetector circuit, the test circuit being configured to generate a testsignal. The test signal simulates the at least one predefinedperturbation. A unitary user input mechanism is coupled to the testcircuit. The unitary user input mechanism is configured to generate theactuation signal in response to a user stimulus and reset the circuitinterrupter assembly in response to a removal of the user stimulus ifthe circuit interrupter is in a tripped state. The tripped state beingindicative of the intervening signal.

In yet another aspect, the present invention is directed to a protectivewiring device for use in an electrical distribution system. The deviceincludes at least one line terminal and at least one load terminalconfigured to be coupled to the at least one line terminal in a resetstate. A detector circuit is coupled to the at least one line terminal.The detector circuit is configured to generate a detection signal inresponse to detecting at least one predefined perturbation in theelectrical distribution system. A circuit interrupter assembly iscoupled between the at least one line terminal and the at least one loadterminal. The circuit interrupter assembly is configured to decouple theat least one line terminal from the at least one load terminal inresponse to the detection signal. An end-of-life mechanism is coupled tothe detector circuit. The end-of-life mechanism is configured topermanently decouple the plurality of line terminals from the pluralityof load terminals in the absence of an intervening signal. A useractuated test mechanism is configured to generate a test signal inresponse to a user stimulus. The test signal simulates the detectionsignal, whereby the circuit interrupter assembly is tripped in responsethereto if the device is operational, a tripped state being indicativeof the intervening signal.

Additional features and advantages of the invention will be set forth inthe detailed description which follows, and in part will be readilyapparent to those skilled in the art from that description or recognizedby practicing the invention as described herein, including the detaileddescription which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary of theinvention, and are intended to provide an overview or framework forunderstanding the nature and character of the invention as it isclaimed. The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate various embodimentsof the invention, and together with the description serve to explain theprinciples and operation of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the electrical device in accordance with anembodiment of the present invention;

FIG. 2 is a detailed perspective view of an end-of-life mechanismemployed in the electrical device depicted FIG. 1;

FIG. 3 is a schematic of the electrical device in accordance with asecond embodiment of the present invention;

FIG. 4 is a detail view of a latch mechanism in accordance with thepresent invention;

FIG. 5 is another view of the latch mechanism of FIG. 4; and

FIG. 6 is yet another view of the latch mechanism of FIG. 4.

DETAILED DESCRIPTION

Reference will now be made in detail to the present exemplaryembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.An exemplary embodiment of the protective device of the presentinvention is shown in FIG. 1, and is designated generally throughout byreference numeral 10.

As embodied herein, and depicted in FIG. 1, a schematic of theelectrical device 10 in accordance with one embodiment of the presentinvention is shown. While the schematic in FIG. 1 is directed to a GFCI,the present invention is equally applicable to AFCIs and/or other suchprotective devices.

Device 10 includes hot line contact 200 and neutral line contact 20coupled to ground fault sensor 100 and grounded neutral sensor 102. Asshown in FIG. 1, the outputs of sensor 100 and sensor 102 are coupled todetector 104. The detector 104 out put (pin 7) is connected to thecontrol input of silicon controlled rectifier (SCR) SCR 106. The wiringdevice 10 includes a tripping mechanism that includes ground faultsensor 100 and grounded neutral sensor 102 coupled to detector 104.Detector 104 is coupled to silicon controlled rectifier (SCR) 106 whichis controlled by detector 104 in accordance with sensor (100, 102)outputs. SCR 106 is coupled to solenoid 52. Solenoid 52 is energizedwhen SCR 106 is turned ON by detector 104. A plunger disposed insolenoid 52 engages latch mechanism 80 to thereby open the contacts incontact assembly 15. Contact assembly 15 is disposed between lineterminals (20, 200), and load terminals (30, 300) and receptacle loadterminals (42, 48). Contact assembly 15 is configured to establishelectrical connectivity between the line terminals (20, 200), and loadterminals (30, 300) and receptacle load terminals (42, 48) when latchmechanism 80 is in a reset state. Contact assembly 15 is configured todisconnect the line terminals (20, 200) from the load terminals (30,300) and receptacle load terminals (42, 48) when latch mechanism 80 isin a tripped state.

With regard to contact mechanism 15, neutral line terminal 20 isconnected to contact member 24 and contact member 28. Contact members 24and 28 are operatively coupled to latch mechanism 80. In other words,contact member 24 connects neutral line terminal 20 to neutral loadfeed-through terminal 30 and contact member 28 connects neutral lineterminal 20 to neutral receptacle contact 42 when the latch mechanism 80is disposed in the reset position. The connectivity is established whencontact member 24 is in electrical continuity with contact 32 andcontact member 28 in electrical continuity with contact member 46. Onthe other hand, when solenoid 52 drives latch mechanism 80 into thetripped position, contact members 24 and 28 are deflected to breakelectrical connectivity with contacts 32 and 46, respectively.

The moveable contact assembly in the hot conductive path is identical.Moveable contact members 240 and 280 mate with fixed contacts 320 and460 respectively. In doing so, they electrically couple/decouple the hotline terminal 200 to hot load feed-through terminal 300 and neutralreceptacle contact 48 depending on whether the latch mechanism 80 is inthe reset state or in the tripped state.

The contact assembly 15 shown in FIG. 1 is representative of what iscommonly referred to as a four-pole contact mechanism. It will beapparent to those of ordinary skill in the pertinent art that contactassembly 15 of the present invention may be of any suitable typedepending on the characteristics of the mechanical implementation of thedevice. For example, contact assembly 15 may employ a cantileveredcontact assembly, a bridge structure, a bus bar arrangement, solid statedevices, or any suitable contact mechanism. In a four-pole arrangement,the receptacle load terminals and the feed-through terminals areelectrically isolated from each other in the tripped state, as well asbeing disconnected from the line terminals.

The contact assembly 15 of the present invention may also be implementedas, what is commonly referred to, a two-pole mechanism. In a two-poleembodiment, contact assembly 15 is similar to the above descriptionexcept that each of the contact pairs 28 and 46, and 280 and 460 arereplaced by a non-interruptible conductive path. As such, receptacleterminal 42 is directly and uninterruptedly connected to load terminal30. This connection is represented by dotted line 43. Likewise,receptacle terminal 48 is directly and uninterruptedly connected to loadterminal 300. This connection is represented by dotted line 49. As thoseof ordinary skill in the art will appreciate, in a two-pole arrangement,while the receptacle load terminals and the feed-through terminals aredisconnected from the line in the tripped state, they are notelectrically isolated from each other in the tripped state.

The contact assembly 15 of the present invention may also be implementedas, what is commonly referred to, a three-pole mechanism. In athree-pole embodiment, contact assembly 15 is similar to the abovedescription except that either contact pair 28 and 46, or 280 and 460are replaced by a non-interruptible conductive path. As such, eitherreceptacle terminal 42 is directly and uninterruptedly connected to loadterminal 30 by way of dotted line 43, or receptacle terminal 48 isdirectly and uninterruptedly connected to load terminal 300 by way ofdotted line 49. As those of ordinary skill in the art will appreciate,while the receptacle load terminals and the feed-through terminals aredisconnected from the line in the tripped state, power cannot beprovided from the load terminals to the feed-through load terminals inthe tripped state in a three-pole arrangement.

Device 10 also includes a reset mechanism 60 coupled to latch mechanism80. As briefly noted above, latch 80 is driven into the tripped state bysolenoid 52. Once the fault is cleared and the user recognizes that thedevice 10 has tripped, the user presses the reset button 60 to restoreservice. When reset button 60 is actuated, latch mechanism 80 closes, orpermits the closure of the contacts disposed in contact assembly 15 torestore AC power to the receptacle load and feed-through load.

Device 10 includes an electronic TEST button 50. Latch mechanism 80 isdriven into the tripped position when test button 50 is depressed by auser, if device 10 is operating properly. In particular, as theschematic of FIG. 1 suggests, a differential current simulating a groundfault is generated when the electrical TEST button 50 is actuated by theuser. Trip solenoid 52 is fired when sensor 100 and detector 104 detecta fault condition. In response thereto, the contacts 32, 46, 320, and460 open, disconnecting the line, load, and receptacle contacts.

The present invention also includes a trip indicator circuit 130. Whendevice 10 is tripped, trip indicator 130 is activated. Trip indicator130 includes components R9, R13, R14, and D1 (LED) which are connectedin parallel with switch S5. When device 10 is tripped, LED D1 isilluminated. However, when the contacts are reset, there is no potentialdifference across the LED and D1 is not illuminated. Those of ordinaryskill in the art will recognize that indicator 130 may include anaudible annunciator as well as an illumination device.

One feature of the present invention relates to the separate EOLfunctionality disposed in end-of-life (EOL) circuit 120. EOL circuit 120includes resistors R19-R25, test button 50, SCR Q4, and diode D5.Resistors R20-R22 and SCR Q4 form a latch circuit. R21 and R22 arearranged in a voltage divider configured to control the operation of Q4.R23 and R24 are coupled to Q4. R23 and R24 are surface-mounted fusibleresistors that control the activation of the EOL mechanism.

The user pushes the TEST button 50 when the GFCI is reset to generate asimulated fault through R25. Concurrently, 120V AC power is applied tofusible resistor R21. If the GFCI is operating properly, sensor 100,detector 104, and other GFCI circuitry will respond to the simulatedfault and trip latch mechanism 80 within about 25 milliseconds. Thesimulated fault current flowing through R25 is terminated even if TESTbutton 50 is still being pushed. As the same time, power is removed fromresistor R21.

If the GFCI circuitry is not operating properly, it will fail to trip inthe manner described above. In response to the continuous application ofAC power, the resistance of fusible R21 increases significantly changingthe value of the R21/R22 voltage divider. In turn, the voltage acrossR20 and R19 becomes sufficient to turn Q4 ON, and current begins to flowthrough resistors R23 and R 24. The resistance values of resistors R23and R24 increase when power is continuously applied for a sufficientduration. The values will increase from several kilo-ohms to values thatare typically greater than 10 meg-ohms. Subsequently, R23 and R24 beginto overheat and the solder that secures R23 and R24 to printed circuitboard 12 fails. After the solder melts, resistors R23 and R24 aredisplaced, actuating EOL contacts 121. When the temperature of resistorsR23, R24 is greater than the threshold, the line terminals (20, 200) aredecoupled from the feed-through load terminals (30, 300) and thereceptacle load terminals (42, 48), independent of the state of circuitinterrupting contacts 15.

Those of ordinary skill in the art will appreciate that becauseresistors R23, R24 are disposed in parallel, they heat independently.Resistor R23 is configured to open one of the EOL contacts 121, whileresistor R24 is configured to independently open the other. In analternate embodiment of the present invention, a single fusible resistoris configured to heat and open both EOL contacts 121.

In an alternate embodiment, device 10 may include TEST button 50′disposed between the power supply and the control input of SCR 106. Whenbutton 50′ is depressed, SCR 106 is turned ON and device 10 is tripped.As such, TEST button 50′ checks the operability of SCR 106 and solenoid52, but not the operability of sensors 100, 102 or detector 104. Thetest signal generated by TEST button 50′ is not a simulation of anexternal fault condition. Switch 50′ simply initiates a current to turnSCR 106 ON. If the SCR 106 turns ON and causes the trip mechanism tooperate, the EOL 120 mechanism is not actuated. If the trip mechanismdoes not operate, EOL 120 will operate.

As shown in FIG. 1, the test button 50 and reset button 60 are separate,user accessible buttons. In an alternative embodiment, the testfunctionality may be incorporated into reset button 60 to create aunitized reset/test button. FIGS. 4-6, described in detail below,provide a mechanical implementation of the combined reset/test button.In FIGS. 4-6, test contacts 5″ are coupled to the reset button, andhence, are not directly accessible to the user. However, test contacts50″ are closed when the unitized button is actuated. On one hand, ifdevice 10 is in the tripped state, the unitized button 60 may bedepressed and released to reset the circuit interrupting contacts 15 inthe manner previously described. Before the device is reset, testcontacts 50″ are closed to activate a test cycle. If the protectivedevice is operational, the circuitry functions normally and the EOLmechanism 120 is not actuated. However, if device 10 is experiencing anEOL condition, the EOL mechanism 120 is actuated, and the load terminalsare permanently disconnected from the line terminals. The EOLdetermination is made each time the unitized button is actuated, whetherto reset the device or to test the device already in the reset state.The periodic testing of the device is typically required to be performedon a monthly basis or before each use of the device. Those skilled inthe art will also appreciate that the test button 50′ (shown in FIG. 1)may also be incorporated into the unitized structure.

As embodied herein and depicted in FIG. 2, a perspective view of the EOLmechanism 120 shown in FIG. 1 is disclosed. Resistors R23 and R24 aresoldered to the underside of printed circuit board (PCB) 12. Openingsare disposed in PCB 12 in alignment with resistors R23 and R24.Resistors R23 and R24 prevent spring loaded plungers 122 from extendingthrough the openings 126 in board 12. Each plunger 122 is configured tosupport an electrically connecting bus-bar member 124. Each bus-bar 124couples a line terminal (20, 200) to the contact assembly 15. Asdescribed above, when the solder supporting R23 and R24 melts, springloaded plungers 122 are driven through the holes, breaking theconnections between the line and load terminals. Once this occurs, thereis no mechanism for resetting the device. Accordingly, the device mustbe replaced. In an alternate embodiment, resistors R23, R24 areconfigured to melt and “burn” open. The result is similar. Spring-loadedplungers 122 are driven through the holes, breaking the connectionsbetween the line and load terminals.

In an alternate embodiment, the EOL mechanism is a single pole mechanismwhich interrupts electrical connectivity either to line terminal 20 orline terminal 200 (not shown.) As those of ordinary skill in the artwill appreciate, in a single-pole arrangement, the opening of the singlepole serves to deny power conveyance from the line to the load.

In yet another alternate embodiment, the end of life mechanism isdisposed between the load terminals and the circuit interrupter as adouble pole mechanism. One pole interrupts electrical connectivitybetween a line terminal and a corresponding feed-through terminal inresponse to an end of life condition. The other pole interruptselectrical connectivity between the line terminal and a correspondingreceptacle terminal in response to the end of life condition.

Referring to FIG. 3, an alternate schematic of the electrical device ofthe present invention is disclosed. This embodiment combines anauto-test circuit with an end-of-life circuit. This design may beemployed in conjunction with any of the embodiments of the invention.This circuit is similar to the circuit depicted in FIG. 1, and theend-of-life circuit/mechanism is similar to that shown above.

Device 10 includes hot line contact 200 and neutral line contact 20coupled to ground fault sensor 100 and grounded neutral sensor 102. Theground fault sensor 100 and grounded neutral sensor 102 are coupled todetector 104. Grounded neutral sensor 102 includes a saturating core 150and a winding 152 coupled to hot and neutral line terminals 200 and 20,respectively. Those of ordinary skill in the art will recognize that itis typical practice to intentionally ground neutral line terminal 20 atthe service panel of the electrical distribution system. During a truegrounded neutral condition, neutral load terminal 30 is inadvertentlygrounded.

A grounded neutral fault condition, and the resulting path throughground by way of terminals 20 and 30, may be simulated by electricalloop 154. When electrical loop 154 is closed, saturating core 150induces current spikes in the electrical loop 154. Reversals in themagnetic field in core 150 corresponded to the zero crossings in the ACpower source. The reversals in the magnetic field generate currentspikes. Current spikes occurring during the negative-transitioning zerocrossings produce a signal during the negative half cycle portions ofthe AC power source. The signal is sensed as a differential signal byground fault sensor 100, and detected by ground fault detector 104. Inresponse, SCR 106 enables solenoid 52 to trip latch mechanism 80.

The simulated grounded neutral condition is enabled when switch 156turns ON, to thereby close electrical loop 154. Control circuit 158turns switch 1560N during the negative half cycle. Thus, the currentspikes occur during the negative half cycle portions but not during thepositive half cycle portions of the AC power signal. Note that whileoutput 162 of ground fault detector 104 attempts to actuate SCR 106, itcannot do so because SCR 106 is reverse biased during the negative halfcycle. As a result, the simulated fault test is unable to turn SCR1060N. However, output signal 162 from ground fault detector 104 is usedby EOL checking circuit 160 to determine whether or not an end of lifecondition has occurred. In response to a true ground fault or groundedneutral condition, ground fault detector 104 signals SCR 106 to actuatesolenoid 52 to trip the latch mechanism 80 during the positive halfcycle portions of AC power source.

In an alternate embodiment, device 10 includes switch 156′ as a meansfor automatically simulating a ground fault. Device 10 may incorporateone or both of these testing features. The ground fault test likewiseoccurs during the negative half cycles of the AC power source. Thoseskilled in the art are familiar with any number of simulated signalsthat may be used by the EOL circuit to determine the operative status ofthe device.

It will be apparent to those of ordinary skill in the pertinent art thatany suitable device may be employed to implement switch 156 (156′). Forexample, switch mechanisms 156 (156′) may be implemented using a MOSFETdevice, such as the device designated as MPF930 and manufactured by ONSemiconductor. In another embodiment, switch 156 (156′) may bemonolithically integrated in the ground fault detector 104.

When a simulated grounded neutral condition is introduced in the mannerdescribed above, a test acceptance signal is provided to delay timer 164during the negative half cycle portions of the AC power source. Delaytimer 164 includes a transistor 166 that discharges capacitor 168 whenthe test acceptance signal is received. Capacitor 168 is recharged bypower supply 170 by way of resistor 172 during the remaining portion ofthe AC line cycle. Again, if there is an internal failure in GFCI 10,the test acceptance signal will not be generated and transistor 166 willnot be turned ON. As a result, capacitor 168 continues to charge untilit reaches a predetermined voltage. At the predetermined voltage, SCR174 is activated during a positive half cycle portion of the AC powersource signal. In response, solenoid 52 drives latch mechanism 80 intothe tripped state.

Note that both ground fault detector 104 and checking circuit 160 derivepower from power supply 170. Redundant components may be added such thatif one component has reached end of life, another component maintainsthe operability of ground fault detector 104, thereby enhancingreliability, or at least assuring the continuing operation of thechecking circuit 160. For example, resistor 172 in power supply 170 maybe equipped with parallel resistors. As another example, resistor 176may be included to prevent the supply voltage from collapsing in theevent the ground fault detector 104 shorts out. Clearly, if the supplyvoltage collapses, delay timer 168 may be prevented from signaling anend of life condition. The present invention should not be construed asbeing limited to the aforementioned examples as those of ordinary skillin the art will recognize that there are a number of redundantcomponents that can be included in device 10.

Checking circuit 160 is ineffectual if latch mechanism 80 and/orsolenoid 52 is experiencing an end of life condition. For example,solenoid 52 may have an electrical discontinuity. This failure mode maybe obviated by the present invention by connecting SCR 174 toend-of-life resistors R23, R24 instead of being connected to solenoid52. This embodiment is shown by dotted line 178. Of course, EOLresistors R23, R24 have been previously described. At end of life, SCR174 conducts current through R23, R24 to cause them to fail, causing EOLcontacts 121 to permanently disconnect the line terminals from the loadterminals.

Dislodging of resistors R23, R24 results in a permanent decoupling ofthe load side of device 10 from the AC power source. Accordingly, it isimportant that the dislodgement (or burn out) of the resistors onlyoccur in response to a true EOL condition, and not due to some spuriouscircumstance, such as transient electrical noise. For example, SCR 174may be turned ON in response to a transient noise event. However,coupling diode 180 may be included to decouple resistor R23, R24 in theevent of a false EOL condition. When SCR 174 is ON, coupling diode 180allows SCR 174 to activate solenoid 52. Latch mechanism 80 trips,whereupon resistors R23, R24 are decoupled from the AC power source. Asin the previous embodiment, device 10 includes a trip indicator 182,which may be an audible and/or visible indicator.

The present invention may include an EOL indicator that is activatedwhen device 10 has reached end-of-life. EOL indicator 183 is disposedacross contacts 121. Of course, there is no potential difference betweencontacts 121 before an end-of-life condition has occurred. However, whencontacts 121 open in response to an end-of-life condition, EOL indicator183 is activated. Those of ordinary skill in the art will recognize thatindicator 183 may include an audible annunciator as well as anillumination device. Indicator 183 emits a steady output at end-of-life,or a non-steady output such as a beeping sound or a flashing light.

Referring to FIG. 4, a detail view of latching mechanism 80 inaccordance with one embodiment of the present invention is disclosed. InFIG. 4, contact 24, disposed on neutral line cantilever 21, is separatedfrom dual load cantilever contact 32, and fixed receptacle contact 46 ina tripped state. Of course, neutral line cantilever 21 is coupled toneutral line terminal 20. Dual load cantilever contact 32 is connectedto cantilever 31, which in turn is connected to neutral feed-throughterminal 30. Reset is effected by applying a downward force to resetbutton 60. Shoulder 1400 on reset pin 824 bears downward. In theembodiment depicted in FIG. 4, TEST contacts 50′ (50″) are shown. Thoseof ordinary skill in the art will recognize that latch mechanism 80 andreset mechanism 60 may be implemented without incorporating testcontacts 50′ (50″). However, in FIG. 4, pin 824 bears down on switch50′(50″) to effect a TEST cycle.

In FIG. 5, neutral line contact 24, load contact 32, and fixedreceptacle contact 46 are still separated. On the other hand, switch 50′(50″) is fully closed to generate the simulated fault condition. Thesimulated fault signal is sensed and detected, causing solenoid 52 toactivate armature 51. Armature 51 moves in the direction shown,permitting hole 828 in latch 826 to become aligned with shoulder 1400.The downward force applied to unitized button 60 causes shoulder 1400 tocontinue to move downward, since it is no longer restrained by shoulder1400.

Referring to FIG. 6, since shoulder 1400 is disposed beneath latch 826,it is no longer able to apply a downward force on latch 826.Accordingly, switch 50′ (50″) opens causing the TEST signal to cease. Asa result, solenoid 52 is de-energized. Armature 51 moves in thedirection shown in response to the biasing force of spring 834 and latch826 is seated on latching escapement 830. In FIG. 6, the motion is shownin mid-process, i.e., contact 24 and 32 are not vet closed; however,device 10 is ultimately fully reset, closing contacts 24, 32, and 46.Further, the EOL mechanism 120 has not been activated because switch 50′(50″) is only closed for the time it takes to trip device 10, i.e.,about 25 milliseconds. This is too short a period of time to actuate theEOL mechanism.

On the other hand, if the circuitry of protective device 10 isexperiencing an EOL condition, armature 51 fails to move in response toclosure of switch 50′ (50″). Shoulder 1400 continues to maintain closureof switch 50′ (50″) for a duration substantially greater than theexpected trip time of the device, i.e., at least 500 milliseconds.Accordingly, the EOL mechanism 120 is configured to activate in themanner previously described. If the latch mechanism 80 of protectivedevice 10 is experiencing an EOL condition, for example, theimmobilization of armature 51 or latch 826 as the result of dirt orcorrosion, switch 50′(50″) will remain closed for a durationsubstantially greater than the expected trip time of the device.Accordingly, device 10 is responsive to EOL conditions in the GFCIcircuitry as well as mechanical EOL conditions.

If switch 50′ (50″) is provided, the latch mechanism 80 may be trippedby way of a user accessible button (not shown) that is coupled to latch826. When the button is depressed, latch 826 moves in the directionshown in FIG. 5 thus causing the mechanism to trip. As has beendescribed above, resetting of latch mechanism 80 may then beaccomplished by depressing reset button 60.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the spirit and scope of the invention. Thus, itis intended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A protective wiring device for use in an electrical distributionsystem, the device comprising: a plurality of line terminals; aplurality of load terminals configured to be coupled to the plurality ofline terminals in a reset state; a detector circuit coupled to theplurality of line terminals, the detector circuit being configured togenerate a detection signal in response to detecting at least onepredefined perturbation in the electrical distribution system; a circuitinterrupter assembly coupled between the plurality of line terminals andthe plurality of load terminals, the circuit interrupter assembly beingconfigured to decouple the plurality of line terminals from theplurality of load terminals in response to the detection signal; and anend-of-life mechanism coupled to the detector circuit, the end-of-lifemechanism being configured to permanently decouple the plurality of lineterminals from the plurality of load terminals independently from thecircuit interrupter in the absence of an intervening signal.
 2. Thedevice of claim 1, wherein the end-of-life mechanism further comprises:a test circuit coupled to the detector circuit, the test circuit beingconfigured to generate a test signal; and a checking circuit coupled tothe detector circuit, the checking circuit being configured to generatethe intervening signal in response to the detection signal.
 3. Thedevice of claim 2, wherein the test signal simulates the at least onepredefined perturbation.
 4. The device of claim 2, wherein the testsignal is a periodic signal.
 5. The device of claim 4, wherein the testsignal occurs during a predetermined polarity of a source voltagepropagating in the electrical distribution system.
 6. The device ofclaim 2, wherein the test signal is automatically generated by the testcircuit.
 7. The device of claim 2, wherein the test circuit isconfigured to generate the test signal in response to a user stimulus.8. The device of claim 7, wherein the test signal simulates the at leastone predefined perturbation.
 9. The device of claim 7, wherein the testsignal does not simulate the at least one predefined perturbation. 10.The device of claim 1, wherein the end-of-life mechanism includes: atimer circuit that is configured to generate an end-of-life enablesignal after a predetermined period of time elapses, the timer circuitbeing reset by the intervening signal; at least one fusible resistorbeing configured to conduct an electrical current in response to theend-of-life enable signal, the at least one fusible resistor beingconfigured to open a predetermined period of time after conducting theelectrical current; a spring member coupled to the at least one fusibleresistor, the spring member being compressed by the at least one fusibleresistor when in a closed state, the spring member also being releasedin response to the at least one fusible resistor being opened; and endof life contacts coupled between at least one of the plurality of lineterminals and at least one of the plurality of load terminals, the endof life contacts being configured to permanently decouple the pluralityof line terminals from the plurality of load terminals in response tothe spring member being released.
 11. The device of claim 10, whereinthe at least one fusible resistor is held in place by a material, thematerial being configured to melt in response to the electrical current.12. The device of claim 11, wherein the material includes a solder or anadhesive.
 13. The device of claim 10, wherein the at least one fusibleresistor is configured to burn open in response to thermal energygenerated by the electrical current.
 14. The device of claim 1, whereinthe at least one predefined perturbation is representative of a groundfault, a grounded neutral, and/or an arc fault.
 15. The device of claim1, further comprising an indicator coupled to the end-of-life mechanism,the indicator being energized in response to the end-of-life mechanismpermanently decoupling at least one of the plurality of line terminalsfrom at least one of the plurality of load terminals.
 16. The device ofclaim 1, further comprising: a test circuit coupled to at least one ofthe detector circuit, the test circuit being configured to generate atest signal simulating the at least predefined perturbation; and acircuit element coupled between the end-of-life mechanism and theplurality of load terminals, the circuit element being configured totransmit an AC power signal or the intervening signal from the pluralityof load terminals to the end-of-life mechanism, the intervening signalbeing substantially equal to zero volts.
 17. The device of claim 16,wherein the end of life mechanism further comprises: at least onefusible resistor coupled to the test circuit and configured to conductan electrical current in response to the test signal, the at least onefusible resistor being configured to open a predetermined period of timeafter conducting the electrical current; a spring member coupled to theat least one fusible resistor, the spring member being compressed by theat least one fusible resistor when in a closed state, the spring memberalso being released in response to the at least one fusible resistorbeing opened; and end of life contacts coupled between at least one ofthe plurality of line terminals and at least one of the plurality ofload terminals, the end of life contacts being configured to permanentlydecouple the at least one of the plurality of line terminals from the atleast one of the plurality of load terminals in response to the springmember being released.
 18. The device of claim 17, wherein the testsignal is generated by a user stimulus.
 19. The device of claim 17,wherein the at least one fusible resistor is held in place by amaterial, the material being configured to melt in response to theelectrical current.
 20. The device of claim 19, wherein the materialincludes a solder or an adhesive.
 21. The device of claim 17, whereinthe at least one fusible resistor is configured to burn open in responseto thermal energy generated by the electrical current.
 22. The device ofclaim 16, wherein the circuit interrupter further includes a resetmechanism coupled to the test circuit, and wherein the test circuitincludes test switch contacts, the reset mechanism being configured toclose the test switch contacts in response to a user stimulus.
 23. Thedevice of claim 22, wherein the reset mechanism further comprises amechanical barrier coupled to the test switch contacts, the mechanicalbarrier being decoupled from the test switch contacts when the circuitinterrupter is tripped, whereby the test signal is discontinued.
 24. Thedevice of claim 1, further comprising: a test circuit coupled to thedetector, the test circuit being configured to generate a test signalsimulating the at least one predefined perturbation in response to anactuation signal; and a unitary user input mechanism coupled to the testcircuit, the unitary user input mechanism being configured to generatethe actuation signal in response to a user stimulus and reset thecircuit interrupter assembly in response to a removal of the userstimulus if the circuit interrupter is in a tripped state, the trippedstate being indicative of the intervening signal.
 25. The device ofclaim 24, wherein the end of life mechanism permanently decouples theplurality of line terminals from the plurality of load terminals if thecircuit interrupter remains in the reset state, the reset state beingindicative of the absence of the intervening signal.
 26. The device ofclaim 1, further comprising a user actuated test mechanism configured togenerate a test signal in response to a user stimulus, the test signalsimulating the detection signal, whereby the circuit interrupterassembly is tripped in response thereto if the device is operational, atripped state being indicative of the intervening signal.
 27. The deviceof claim 26, wherein the end of life mechanism permanently decouples atleast one of the plurality of line terminals from at least one of theplurality of load terminals if the circuit interrupter remains in thereset state, the reset state being indicative of the absence of theintervening signal.
 28. The device of claim 1, wherein the end-of-lifemechanism is coupled to the circuit interrupter assembly such that thepermanently decoupling is prevented whenever the circuit interrupter hasdecoupled the plurality of line terminals from the plurality of loadterminals.
 29. A protective wiring device for use in an electricaldistribution system, the device comprising: at least one line terminal;at least one load terminal configured to be coupled to the line terminalin a reset state; a detector circuit coupled to the at least one lineterminal, the detector circuit being configured to generate a detectionsignal in response to detecting at least one predefined perturbation inthe electrical distribution system; a circuit interrupter assemblycoupled between the at least one line terminal and the at least one loadterminal, the circuit interrupter assembly being configured to decouplethe at least one line terminal from the at least one load terminal inresponse to the detection signal; an end-of-life mechanism coupled tothe detector circuit, the end-of-life mechanism being configured topermanently decouple the at least one line terminal from the at leastone load terminal independently from the circuit interrupter assembly inthe absence of an intervening signal; a test circuit coupled to thedetector circuit, the test circuit being configured to generate a testsignal, the test signal simulating the at least one predefinedperturbation; and a checking circuit coupled to the detector circuit,the checking circuit being configured to generate the intervening signalin response to the detection signal.
 30. A protective wiring device foruse in an electrical distribution system, the device comprising: atleast one line terminal; at least one load terminal configured to becoupled to the line terminal in a reset state; a detector circuitcoupled to the at least one line terminal, the detector circuit beingconfigured to generate a detection signal in response to detecting atleast one predefined perturbation in the electrical distribution system;a circuit interrupter assembly coupled between the at least one lineterminal and the at least one load terminal, the circuit interrupterassembly being configured to decouple the at least one line terminalfrom the at least one load terminal in response to the detection signal;an end-of-life mechanism coupled to the detector circuit, theend-of-life mechanism being configured to permanently decouple the atleast one line terminal from the at least one load terminalindependently from the circuit interrupter assembly in the absence of anintervening signal; a test circuit coupled to the detector circuit, thetest circuit being configured to generate a test signal simulating theat least one predefined perturbation; and a circuit element coupledbetween the end-of-life mechanism and the at least one load terminal,the circuit element being configured to transmit the intervening signalfrom the at least one load terminal to the end-of-life mechanism, theintervening signal being substantially equal to zero volts.
 31. Aprotective wiring device for use in an electrical distribution system,the device comprising: at least one line terminal; at least one loadterminal configured to be coupled to the at least one line terminal in areset state; a detector circuit coupled to the at least one lineterminal, the detector circuit being configured to generate a detectionsignal in response to detecting at least one predefined perturbation inthe electrical distribution system; a circuit interrupter assemblycoupled between the at least one line terminal and the at least one loadterminal, the circuit interrupter assembly being configured to decouplethe at least one line terminal from the at least one load terminal inresponse to the detection signal; an end-of-life mechanism coupled tothe detector circuit, the end-of-life mechanism being configured topermanently decouple the at least one line terminal from the at leastone load terminal independently from the circuit interrupter assembly inthe absence of an intervening signal; a test circuit coupled to thedetector, the test circuit being configured to generate a test signalsimulating the at least one predefined perturbation in response to anactuation signal; and a unitary user input mechanism coupled to the testcircuit, the unitary user input mechanism being configured to generatethe actuation signal in response to a user stimulus and reset thecircuit interrupter assembly in response to a removal of the userstimulus if the circuit interrupter is in a tripped state, the trippedstate being indicative of the intervening signal.
 32. The device ofclaim 31, wherein the end of life mechanism permanently decouples theplurality of line terminals from the plurality of load terminals if thecircuit interrupter remains in the reset state, the reset state beingindicative of the absence of the intervening signal.
 33. A protectivewiring device for use in an electrical distribution system, the devicecomprising: a plurality of line terminals; a plurality of load terminalsconfigured to be coupled to the plurality of line terminals in a resetstate; a detector circuit coupled to the plurality of line terminals,the detector circuit being configured to generate a detection signal inresponse to detecting at least one predefined perturbation in theelectrical distribution system; a circuit interrupter assembly coupledbetween the plurality of line terminals and the plurality of loadterminals, the circuit interrupter assembly being configured to decouplethe plurality of line terminals from the plurality of load terminals inresponse to the detection signal; an end-of-life mechanism coupled tothe detector circuit, the end-of-life mechanism being configured topermanently decouple the at least one line terminal from the at leastone load terminal independently from the circuit interrupter assembly inthe absence of an intervening signal; and a user actuated test mechanismconfigured to generate a test signal in response to a user stimulus, thetest signal simulating the detection signal, whereby the circuitinterrupter assembly is tripped in response thereto if the device isoperational, a tripped state being indicative of the intervening signal.34. The device of claim 33, wherein the end of life mechanismpermanently decouples the plurality of line terminals from the pluralityof load terminals if the circuit interrupter remains in the reset state,the reset state being indicative of the absence of the interveningsignal.